MAGNETRON-SPUTTERED HARD MATERIAL COATINGS ON THERMOPLASTIC POLYMERS FOR CLEAN ROOM APPLICATIONS

Even under demanding environments, such as clean rooms, polymers are a lready used in different ranges of applications. The wear and particle generation within a specific particle size under mechanical stress is a limiting factor, as are high material and cleaning costs. Building on this state-of-the-art basis, our aim was to develop an innovative m aterial concept that would allow the application of a thermoplastic po lymer coated with a thin hard material (thickness up to 2.5 mu m). The refore, it was necessary to improve the wear resistance, the adherence between the polymer and the coating as well as to reduce the interact ion with the aluminum (A6061) counterbody which functions as the tribo logical partner in the application. To align the aims and economics of the project, the production process consisted of only two phases: fir st, the injection moulding process that was then followed by a MSIP pr ocess including a plasma pretreatment. In this investigation, poly(but yleneterephthalate) (PBT), poly(amide) 6.6 (PA 6.6) and poly(carbonate ) PC were chosen as substrate material. The coating materials presente d here were based on titanium (Ti-N). The thin films were deposited by magnetron sputter ion plating (MSIP) because of its low defect rate a nd wide range of parameter variation possibilities to reduce the therm al stress during the coating process. The process parameter's influenc e on the microstructure, extending from amorphous to columnar (crystal line) as well as the film thickness were analysed by SEM. Selected res ults of different plasma pretreatments to improve the adhesion for spe cific polymers will be discussed and presented. It will be shown that it is possible to improve the adherence between the film and the plast ic substrate and to reduce the particle generation after the appropria te etching and coating process has taken place. (C) 1998 Elsevier Scie nce S.A. All rights reserved.